1. Field of the Invention
The present invention relates to a method and an apparatus for forming an image by electrophotography, wherein the image is fixed on the recording medium by a heating device, and which permits a new printing job to be started in a relatively short time after the last printing job.
2. Discussion of the Related Art
A recording or printing apparatus adapted to form an image by electrophotography is known, wherein a visible image is fixed on a recording medium under heat generated by an image fixing heating device. In one type of such image forming apparatus, a scanner motor of a scanning unit for generating a latent image is turned off immediately after each printing operation or job, and the temperature of the heating device is held at a stand-by temperature lower than a predetermined image fixing temperature for a predetermined time period after the last printing job. In another type of such apparatus, the scanner motor is kept on, and the temperature of the heating device is held at the image fixing temperature even after the last printing job is completed, so that a new printing job may be started in a short time after the last printing job.
In the former type of electrophotographic image forming apparatus, when a print start command for a new printing job is received within the predetermined time period after the last printing job, the new printing job cannot be started until the scanner motor is turned on and accelerated to the predetermined nominal operating speed and until the temperature of the heating device is raised to the image fixing temperature. Accordingly, it takes a relatively long time for the new printing job to be started after the last printing job.
In the latter type of apparatus, the temperature of the heating device may be held at the relatively high image fixing temperature for a long time without a printing operation being performed after the last printing job. This means a waste of electric power in maintaining the heating device at the relatively high image fixing temperature, due to a long stand-by time without a print start command being received after the last printing job. Further, this arrangement tends to raise the temperature within the apparatus to a high level, whereby the apparatus may be adversely influenced by the heat. For instance, a laser output of the scanner unit may be undesirably lowered due to the heat generated by the heating device while the apparatus is in a stand-by state without a print start command being received.